But there is a difference between having an opinion on something and how you act about that opinion. Supporters of Prop 8, whether their ideas were unfounded or not, were opposed to redefining an existing social construct. It's pretty likely that if it had been the polygamist community that had gained a bunch of support and were pushing forward polygamy equality that the same group of people would have been doing the same things they were doing. It really has nothing to do with the people, it's about the movement against a social construct they agree with.We’re not talking about just any opinion. You’re not announcing a position on Neptune, or asparagus. You have an opinion about people, and your opinion is specifically that you oppose what they do and you believe they are sinful.
It is dishonest to talk badly about people and then act as though you were saying something totally neutral. No matter how carefully you word the unkindness, it is still there.
It's also not that silly to think that some people will think something that someone else does is wrong, regardless of what it is. There are people that dislike others because they eat asparagus. There are people that dislike others because they mow their lawn three times a day.
There is not a fine line between what constitutes discrimination or makes certain opinions okay. Demonizing others because of how they feel on certain topics only reaffirms their positions, it doesn't convince them to change. As TWD rightly pointed out above, there is a huge disconnect between what the vocal gay rights advocates are saying ("It doesn't affect you, live and let live!") and what they are doing ("If you have a problem with us you're no better than the people who lynched blacks and we will treat you as such!").